Biology subjects

Lang, A.

Publications and source records attributed to Lang, A..

At least 19 recordsLinked to original sources

bioRxiv2026

Exposure to childhood adversity and adult alcohol, nicotine, and illicit drug use in Germany: a cross-sectional analysis of the German National Cohort (NAKO)

Rationale: Exposure to adversity in childhood and adolescence (i.e., "early-life stress"; ELS) is a well-established risk factor for substance use. Objectives: The aim of this study was to investigate associations between ELS exposure and substance use across subtypes of ELS, different substance classes, and behavioral profiles of substance use. Methods: In this cross-sectional study, we examined associations between ELS exposure and substance use in a population-based sample of 172,173 adults aged 19-74 years from the German National Cohort (NAKO). ELS exposure was assessed using the Childhood Trauma Screener. Substance use included nicotine, alcohol, and illicit drug use. Associations were examined using regression models evaluating overall ELS exposure, cumulative trauma load, and ELS subtypes. Latent class analysis (LCA) was conducted to identify substance use profiles. Results: ELS exposure was associated with higher odds of smoking, greater smoking severity, heavier alcohol consumption among drinkers, and higher odds of lifetime illicit drug use. Overall, the strongest associations were observed for opioid and stimulant use. Dose-response analyses revealed higher risk with increasing numbers of ELS subtypes. Abuse-related subtypes, particularly exposure to physical and sexual abuse, consistently showed strongest independent associations across substances, whereas neglect exhibited weaker, more variable associations. LCA identified four substance use profiles, with ELS exposure predicting membership in more severe polysubstance classes. Conclusions: ELS emerged as a robust risk factor for adult substance use, underscoring the need for trauma-informed approaches in clinical practice, public health, and policy to mitigate the long-term consequences of early adversity.

neuroscience↗

bioRxiv2026

CB2 activation during epileptogenesis recruits immunomodulatory monocytes and mitigates cognitive, affective and seizure outcomes

Temporal lobe epilepsy (TLE) is frequently associated with severe cognitive impairment and psychiatric comorbidities that are highly disabling and not targeted by anti-seizure medications, highlighting the need for therapies that target epileptogenesis rather than merely suppress seizures. Despite strong evidence implicating neuroinflammation in this process, anti-inflammatory approaches have not yielded such therapies yet. Infiltrating peripheral monocytes are widely viewed as detrimental amplifiers of post-status epilepticus (SE) inflammation, although emerging data suggest context-dependent protective roles. The cannabinoid receptor type 2 (CB2), highly expressed in myeloid cells, represents a potential immunomodulatory target linking leukocyte recruitment and inflammatory polarization. Using a juvenile rat model of TLE, we characterized hippocampal neuroinflammation and CB2 expression during epileptogenesis and evaluated the effects of transient CB2 activation with the selective agonist GP1a. SE induced a rapid but transient inflammatory response and robust recruitment of peripheral monocytes that persisted as anti-inflammatory monocyte-derived macrophages. CB2 activation did not suppress early cytokine induction but selectively enhanced recruitment of anti-inflammatory monocytes and modestly increased anti-inflammatory signaling. Importantly, transient CB2 stimulation preserved synaptic plasticity, improved cognitive performance, reduced anxiety-like behavior, and delayed seizure onset. These findings identify CB2-dependent modulation of peripheral myeloid cells as a potential disease-modifying axis in TLE.

neuroscience↗

bioRxiv2026

Automatic pain face analysis in mice: Applied to a varied dataset with non-standardized conditions

Biomedical research relies on scientifically validated tools to assess pain, suffering, and distress in laboratory animals to ensure their well-being. In mice, the most frequently used laboratory animals, the Mouse Grimace Scale (MGS) provides a reliable tool for the assessment of facial expression changes caused by impaired well-being. However, no automated tool can yet reliably assess all features of the MGS across different mouse strains under varying experimental or housing conditions in real-time, as the variability present in recorded image datasets poses substantial challenges for computer vision models. Despite this technical difficulty, variability across subsets in terms of mouse strain, treatments, laboratory, and image acquisition setup is essential for paving the way toward MGS assessment under non-standardized conditions in the home cage rather than standardized cage-side recording setups. Against this background, a large and diverse dataset containing five subsets is introduced and a deep learning model was trained to predict the average MGS scores ranging between 0 and 2. It achieved a root mean squared error (RMSE) of 0.26 when trained on all subsets of the dataset, outperforming the average human rater in terms of error magnitude. The correlation between human raters and automated MGS scores was very high (Pearsons r=0.85). In the cross-dataset evaluation, one subset was excluded from training and used for testing the model. This approach yielded higher errors compared to models trained and tested on the same subsets. A model restricted to the feature of orbital tightening showed lower performance than one trained on all facial features of the MGS. Overall, the most reliable model for predicting average MGS scores for a novel dataset is the one trained on the combined subsets. Performance may be further enhanced by fine-tuning the model using human-generated MGS scores for a portion of the novel subset.

animal behavior and cognition↗

bioRxiv2025

Retrograde mitochondrial transport regulates mitochondrial biogenesis in zebrafish neurons

To maintain a functional mitochondrial population in a long-lived cell like a neuron, mitochondria must be continuously replenished through the process of mitochondrial biogenesis. Because most mitochondrial proteins are nuclear encoded, mitochondrial biogenesis requires communication between mitochondria and the nucleus. This can be a challenge in a large, compartmentalized cell like a neuron in which a large portion of the mitochondrial population is in neuronal compartments far from the nucleus. Using in vivo assessments of mitochondrial biogenesis in zebrafish neurons, we determined that mitochondrial transport between distal axonal compartments and the cell body is required for sustained mitochondrial biogenesis. Estrogen-related receptor transcriptional activation links transport with nuclear expression of mitochondrial genes. Together, our data support a role for retrograde feedback between axonal mitochondria and the nucleus for regulation of mitochondrial biogenesis in neurons.

neuroscience↗

bioRxiv2025

Reducing the CAV1-dependent trafficking of G6PC1 in the liver protects against the development of type 2 diabetes

Targeting hepatic gluconeogenesis is an efficient strategy to counteract the development of type 2 diabetes. Hepatic glucose production into the bloodstream is controlled by the GLUT2 transporter and a vesicular pathway dependent on Caveolin-1 (CAV1) involving G6PC1 location at the plasma membrane. We hypothesized that decreasing hepatic gluconeogenesis by targeting CAV1 specifically in the liver (L.Cav1-/- mice) improves energy and glucose metabolism in diabetic mice. Here we show that the absence of hepatic CAV1 increases insulin sensitivity, glucose tolerance and decreases fasting hyperglycemia and hyperinsulinemia in mice feeding a high fat high sucrose diet (HFHS diet). The decrease in insulin sensitivity takes place also in L.Cav1-/- mice feeding a standard diet (STD diet). Moreover, we demonstrated an improvement of glycemic control when hepatic Cav1 is deleted in previously prediabetic mice. In parallel, the absence of CAV1 in the liver reduces body weight gain and lipid intestinal absorption. Together these findings highlight that the vesicular pathway of glucose production represents a promising therapeutic target in the prevention of type 2 diabetes.

physiology↗

bioRxiv2025

Large extracellular vesicles derived from red blood cells in coronary artery disease patients with anemia promote endothelial dysfunction

Background and purposeEndothelial dysfunction (ED) is a hallmark of cardiovascular disease (CVD). We recently showed that anemia is associated with worsening of endothelial function after acute myocardial infarction (AMI). Extracellular vesicles (EVs) are efficient communicators between cells and can functionally contribute to different CVD, including, AMI. However, their specific role of EVs in stable coronary artery disease (CAD)-associated with anemia, particularly their contribution to ED, has not yet been investigated systematically. Experimental approachRed blood cell-derived EVs (REVs) and plasma-derived EVs (PLEVs) from all blood cells and endothelium were isolated from patients with stable CAD. The isolated large REVs and PLEVs were characterized using dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), transmission electron microscopy (TEM), and Western blotting. Uptake assays were performed by co-incubating with fluorescently-labeled REVs and PLEVs with human umbilical vein endothelial cells (ECs). Nitric oxide (NO) consumption ability of REVs was analyzed using a chemiluminescence detector (CLD). After co-incubation of aortic rings explanted from wild-type (WT) mice with REVs and PLEVs from anemic and non-anemic CAD patients, endothelial function was assessed using a wire myograph system. To investigate differences in the content of REVs and PLEVs between anemic and non-anemic CAD patients, proteomic analysis was performed. Key resultsDLS analysis showed that both REVs and PLEVs were within the size distribution range of 100-1000 nm. NTA analysis revealed increased release of REVs in anemic patients compared to non-anemic patients. Co-incubation of labeled REVs and PLEVs with ECs demonstrated their uptake by ECs in vitro which was similar between anemic patients compared to non-anemic patients. REVs from anemic patients showed increased NO consumption compared to those from non-anemic patients. Aortic rings co-incubated with REVs from anemic patients showed attenuated endothelial NO-dependent relaxation responses compared to non-anemic patients. Proteomics analysis of REVs from anemic patients revealed numerous differentially expressed proteins, including decreased abundance of antioxidant proteins such as catalase 1 (CAT1), superoxide dismutase 1 (SOD1) and increased oxidative stress-promoting myeloperoxidase (MPO). Co-incubation of ECs with REVs from anemic patients demonstrated increased ROS production. ConclusionAnemia is associated with increased release of REVs and enhanced NO consumption, which promotes ED. This is further exacerbated by an altered redox balance and increased ROS production, implicating therapeutic importance in anemic patients with CAD. Graphical AbstractAnemia is associated with an increased release of RBC-derived large extracellular vesicles (REVs), which are taken up by endothelial cells (ECs). Anemic REVs show enhanced nitric oxide (NO) consumption, contributing to NO dysregulation in ECs. Additionally, REVs carry various redox enzymes, including the oxidative stress-promoting enzyme myeloperoxidase (MPO), as well as antioxidant enzymes such as superoxide dismutase (SOD) and catalase (CAT). An imbalance in these redox enzymes leads to increased oxidative stress and endothelial nitric oxide synthase (eNOS) uncoupling, resulting in impaired NO-mediated relaxation responses and subsequent endothelial dysfunction (ED). O_FIG O_LINKSMALLFIG WIDTH=166 HEIGHT=200 SRC="FIGDIR/small/642191v1_ufig1.gif" ALT="Figure 1"> View larger version (24K): org.highwire.dtl.DTLVardef@19d4cccorg.highwire.dtl.DTLVardef@1d1b3forg.highwire.dtl.DTLVardef@e7f144org.highwire.dtl.DTLVardef@190b007_HPS_FORMAT_FIGEXP M_FIG C_FIG

physiology↗

bioRxiv2025

Local erythropoiesis directs oxygen availability in bone fracture repair

Oxygen tension dynamically regulates stem cell fate and tissue regeneration, yet how local oxygen availability is controlled within the bone marrow niche remains poorly understood. While bone marrow injury, such as by bone fracture, disrupts marrow vasculature, the consequences on local oxygen tension remain unclear. Here, we show in mice that while the tissue oxygen tension in bone marrow is low (25 mmHg, [~]4% O2), intracellular oxygenation is heterogeneous and erythroid cells are high in oxygen. Bone fracture elevates oxygen tension in the injured bone marrow (>55 mmHg, [~]8%), which persists for over a week post-injury. This oxygen elevation results not from angiogenesis, but rather from localized expansion of erythroid precursor cells in the injured bone marrow. The activated erythroid precursors synthesize hemoglobin and accumulate oxygen, acting as local modulators of oxygen tension. Blocking transferrin receptor 1 (CD71)-mediated iron uptake impairs hemoglobin synthesis, reduces local oxygen levels, and enhances bone regeneration through increased angiogenesis and osteogenesis. These findings identify erythroid precursors as active regulators of local oxygen availability in the bone marrow niche, which may be targetable to enhance tissue regeneration.

cell biology↗

bioRxiv2025

Brain Infiltrated Monocyte-Macrophages in a rat model of Temporal Lobe Epilepsy: Revisiting the Pro-Inflammatory Paradigm

Neuroinflammation is central to temporal lobe epilepsy, yet the specific role of myeloid cells remains unclear. In status epilepticus (SE) models, circulating monocytes have been reported to infiltrate the brain, though distinguishing them from microglia remains challenging. Using a rat model, we traced infiltrating monocytes post-SE, to investigate their persistence, phenotypic evolution during epileptogenesis and contribution to neuroinflammation. By tracking phagocyted fluorescent nanoparticles and using CD68 immunohistochemistry, we confirmed that monocytes entered the brain in significant numbers 24 hours post-SE, after the inflammatory peak occurred (7h post-SE). Tracked up to 7 weeks, these cells adopted a microglia-like phenotype, contributed to the microglial scar and sustained low-grade inflammation during the chronic phase of epilepsy solely through their presence, as their expression of pro-inflammatory markers resembled that of non-activated microglia. Importantly, monocytes initially and transiently supported an anti-inflammatory response providing a unique opportunity to modulate neuroinflammation and potentially disrupt epilepsy progression, opening new avenues for therapeutic interventions.

neuroscience↗

bioRxiv2024

YAP regulates periosteal expansion in fracture repair

Bone fracture repair initiates by periosteal expansion. The periosteum is typically quiescent, but upon fracture, periosteal cells proliferate and contribute to bone fracture repair. The expansion of the periosteum is regulated by gene transcription; however, the molecular mechanisms behind periosteal expansion are unclear. Here, we show that Yes-Associated Protein (YAP) and transcriptional co-activator with PDZ-binding motif (TAZ) mediate periosteal expansion and periosteal cell proliferation. Bone fracture increases the number of YAP-expressing periosteal cells, and deletion of YAP and TAZ from Osterix (Osx) expressing cells impairs early periosteal expansion. Mechanistically, YAP regulates both cell-intrinsic and cell-extrinsic factors that allow for periosteal expansion. Specifically, we identified Bone Morphogenetic Protein 4 (BMP4) as a cell extrinsic factor regulated by YAP, that rescues the impairment of periosteal expansion upon YAP/TAZ deletion. Together, these data establish YAP mediated transcriptional mechanisms that induce periosteal expansion in the early stages of fracture repair and provide new putative targets for therapeutic interventions.

cell biology↗

bioRxiv2024

Novel fluorescence-based methods to determine infarct and scar size in murine models of reperfused myocardial infarction

BackgroundDetermination of infarct area and scar size following myocardial infarction (MI) is commonly used to evaluate the efficacy of potential cardioprotective treatments in mice and other animal models. MethodsFor both, early and late time points following MI, we compared classical histochemical approaches with fluorescence staining methods. Reperfused MI was induced in male C57BL/6J mice and hearts were extracted 24 hours, 7-, 21-, or 28-days following MI and stained with 2,3,5-Triphenyltetrazolium chloride (TTC) and Evans Blue, Hoechst, phalloidin, Sirius Red, Massons or Gomoris Trichrome or Wheat Germ Agglutinin (WGA). ResultsFluorescent staining combining Hoechst and phalloidin constitutes an alternative for TTC and Evans Blue, enabling a clear visualization of infarct area, area at risk, as well as remote area unaffected by MI. Infarct size early after reperfusion determined with TTC staining correlates strongly with that demarcated by phalloidin while combination of Hoechst and phalloidin staining can emulate classical TTC/Evans Blue staining 24 h post-MI. Moreover, WGA is equally accurate as the classical Sirius Red, Massons and Gomoris Trichrome stainings in identifying scar size in later phases (>7d) post-MI. Finally, we demonstrate feasibility of combining conventional fluorescence staining by localizing CD45+ leukocytes to specific regions of the infarcted myocardium. ConclusionWe established staining procedure is not inferior to classical TTC staining while providing substantial benefits including the option for unbiased software-assisted analysis while sparing ample residual tissue for additional analyses. Overall, this enhances the data quality and reduces the required animal numbers consistent with the 3R concept of animal experimentation. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=131 SRC="FIGDIR/small/604384v1_ufig1.gif" ALT="Figure 1"> View larger version (36K): org.highwire.dtl.DTLVardef@17ccc83org.highwire.dtl.DTLVardef@56d433org.highwire.dtl.DTLVardef@857f37org.highwire.dtl.DTLVardef@63297d_HPS_FORMAT_FIGEXP M_FIG C_FIG

pathology↗

bioRxiv2024

Cyr61 delivery promotes angiogenesis during bone fracture repair

Compromised vascular supply and insufficient neovascularization impede bone repair, increasing risk of non-union. Cyr61, Cysteine-rich angiogenic inducer of 61kD (also known as CCN1), is a matricellular growth factor that is regulated by mechanical cues during fracture repair. Here, we map the distribution of endogenous Cyr61 during bone repair and evaluate the effects of recombinant Cyr61 delivery on vascularized bone regeneration. In vitro, Cyr61 treatment did not alter chondrogenesis or osteogenic gene expression, but significantly enhanced angiogenesis. In a mouse femoral fracture model, Cyr61 delivery did not alter cartilage or bone formation, but accelerated neovascularization during fracture repair. Early initiation of ambulatory mechanical loading disrupted Cyr61-induced neovascularization. Together, these data indicate that Cyr61 delivery can enhance angiogenesis during bone repair, particularly for fractures with stable fixation, and may have therapeutic potential for fractures with limited blood vessel supply.

bioengineering↗

bioRxiv2024

Maternal characteristics and their relation to early mother-child interaction and cognitive development in toddlers

Early mother-infant interaction is believed to have a significant impact on the social, cognitive, and emotional development of children. These interactions are not only influenced by child and contextual factors but also by the mothers personality traits and strain. In this study, we investigated the relation between maternal factors such as personality, depressive symptoms, or experiencing of emotions, with (i) childrens early cognitive development and (ii) interaction patterns in a sample of 116 mother-child dyads (mean child age = 18.63 months {+/-} 6.42). Maternal factors were assessed using standardized questionnaires, childrens cognitive development was measured using the Bayley Scales of Infant and Toddler Development, and interaction patterns were evaluated using the CARE-Index. The study found that children of mothers who scored higher in agreeableness performed better in cognitive assessments. Additionally, our analysis revealed statistical trends indicating that mothers with higher levels of conscientiousness tended to be less unresponsive in the interaction with their infants, while those with higher levels of neuroticism were more likely to exhibit compulsive behavior in their toddlers. Additionally, there was a trend indicating that maternal depression was associated with increased maternal controlling behavior towards toddlers. Finally, mothers who placed significant importance on their bodily signals to assess their overall well-being had higher scores in the quality of interaction with their child. Overall, these findings show the intricate relation between maternal behavior and state with dyadic interaction quality. This should underline that optimal infant development is only possible if mothers are well supported especially if in need due to various burdens such as depressive symptoms.

developmental biology↗

bioRxiv2023

Identification of SIRT4 as a novel paralog-specific interactor and candidate suppressor of C-RAF kinase in MAPK signaling

Cellular responses leading to development, proliferation, and differentiation rely on RAF/MEK/ERK signaling that integrates and amplifies signals from various stimuli to cellular downstream responses. The clinical significance of C-RAF activation has been reported in many types of tumor cell proliferation and developmental disorders, which requires the discovery of potential C-RAF protein regulators. Here, we identify a novel and specific protein interaction between C-RAF, among the RAF kinase paralogs, and SIRT4 among the mitochondrial sirtuin family members SIRT3, SIRT4, and SIRT5. Structurally, C-RAF binds to SIRT4 through the N-terminal cysteine-rich domain (CRD; a.a. 136-187), and on the other side, SIRT4 requires predominantly the C-terminus (a.a. 255-314) for full interaction with C-RAF. Interestingly, SIRT4 interacts specifically with C-RAF in a pre-signaling inactive (serine 259 phosphorylated) state. Consistent with this finding, ectopic expression of SIRT4 in HEK293 cells results in upregulation of pS259-C-RAF levels and concomitant reduction of MAPK signaling as evidenced by strongly decreased phospho-ERK signals. Thus, our findings propose another extra-mitochondrial role of SIRT4 and suggest that SIRT4 functions as a cytosolic tumor suppressor of C-RAF-MAPK signaling, besides its known metabolic tumor suppressor role towards glutamate dehydrogenase and glutamine levels in mitochondria.

biochemistry↗

bioRxiv2023

RBM39 shapes innate immunity through transcriptional and splicing control of IRF3 and other key factors

RNA-binding motif protein 39 (RBM39) is an RNA-binding protein involved in tumorigenesis, cell metabolism, and development. Here, we performed a genome-wide CRISPR/Cas9 screen in two liver-derived cell lines and identified RBM39 as a regulator of cell intrinsic innate immune responses. The knockdown of RBM39 or the treatment with Indisulam, an aryl sulfonamide drug targeting RBM39 for proteasomal degradation, strongly reduced the induction of interferon-stimulated genes (ISGs) in response to double-stranded RNA (dsRNA) or viral infections upon sensing by toll-like receptor 3 (TLR3) or cytosolic RIG-I-like receptors. RNA sequencing (seq) and mass spectrometry identified that transcription and/or splicing of the key pathway components IRF3, RIG-I, and MDA5 were affected by RBM39 depletion. RBM39 knockdown further restrained type I and type III IFN pathways, by reducing expression of the type I IFN receptor subunit interferon alpha and beta receptor subunit 2 (IFNAR2), type III IFN receptor subunit interleukin 10 receptor subunit beta (IL-10RB) and transcription factor signal transducer and activator of transcription (STAT) 1 and 2. RBM39 overall orchestrates innate immunity by regulating basal expression of key factors of the interferon response via transcription and/or alternative splicing. SignificanceThe function of RBM39 in tumorigenesis has been investigated intensively in the last decade, but its immunological role is still largely unknown. In our study, we identified RBM39 as a regulatory factor of cell intrinsic signaling via a CRISPR/Cas9 screen. Depletion of RBM39 impairs TLR3, RIG-I/MDA5, and IFN pathways, and thus attenuates innate immune responses. Our omics analysis revealed that RBM39 governs the basal expression of several key factors within these pathways, such as RNA sensors RIG-I and MDA5, type I/III receptors, transcription factors IRF3, STAT1 and STAT2, via its transcriptional and splicing function. Therefore, RBM39 might be a therapeutic target to modulate innate immunity, e.g. in the context of autoimmune disorders.

immunology↗

bioRxiv2023

CDK12/CDK13 inhibition disrupts a transcriptional program critical for glioblastoma survival

Glioblastoma is the most prevalent and aggressive malignant tumor of the central nervous system. With a median overall survival of only one year, glioblastoma patients have a particularly poor prognosis, highlighting a clear need for novel therapeutic strategies to target this disease. Transcriptional cyclin-dependent kinases (tCDK), which phosphorylate key residues of RNA polymerase II (RNAPII) c-terminal domain (CTD), play a major role in sustaining aberrant transcriptional programs that are key to development and maintenance of cancer cells. Here, we show that either pharmacological inhibition or genetic ablation of the tCDKs, CDK12 and CDK13, markedly reduces both the proliferation and migratory capacity of glioma cells and patient-derived organoids. Using a xenograft mouse model, we demonstrate that CDK12/13 inhibition not only reduces glioma growth in vivo. Mechanistically, inhibition of CDK12/CDK13 leads to a genome-wide abrogation of RNAPII CTD phosphorylation, which in turn disrupts transcription and cell cycle progression in glioma cells. In summary, the results provide proof-of-concept for the potential of CDK12 and CDK13 as therapeutic targets for glioblastoma. Significance statementGlioblastoma is a common, aggressive, and invasive type of brain tumor that is usually fatal. The standard treatment for glioblastoma patients is surgical resection, radiotherapy, and chemotherapy with DNA-alkylating agents, and unfortunately current treatments only extend overall survival by a few months. It is therefore critical to identify and target additional biological processes in this disease. Here, we reveal that targeting a specific transcriptional addiction for glioma cells by inhibition of CDK12/CDK13 disrupts glioma-specific transcription and cell cycle progression and has potential to provide a new therapeutic strategy for glioblastoma.

cancer biology↗

bioRxiv2023

Corepressor inactivation through tandem linear motif-induced polymerization

While the elucidation of regulatory mechanisms of folded proteins is facilitated due to their amenability to high-resolution structural characterization, investigation of these mechanisms in disordered proteins is more challenging due to their structural heterogeneity, which can be captured by a variety of biophysical approaches. Here, we used the transcriptional master corepressor CtBP, which binds the putative metastasis suppressor RAI2 through repetitive SLiMs, as a model system. Using cryo-electron microscopy embedded in an integrative structural biology approach, we show that RAI2 unexpectedly induces CtBP polymerization through filaments of stacked tetrameric CtBP layers. These filaments lead to RAI2-mediated CtBP nuclear foci and relieve its corepressor function in RAI2-expressing cancer cells. The impact of RAI2-mediated CtBP loss-of-function is illustrated by the analysis of a diverse cohort of prostate cancer patients, which reveals a substantial decrease in RAI2 in advanced treatment-resistant cancer subtypes. As RAI2-like SLiM motifs are found in a wide range of organisms, including pathogenic viruses, our findings serve as a paradigm for diverse functional effects through multivalent interaction-mediated polymerization by disordered proteins in healthy and diseased conditions. The specific properties of these repeated interactions open up new therapeutic opportunities.

molecular biology↗

bioRxiv2023

Modulation of functional phosphorylation sites by basic residues in the Unique domain of c-Src

In contrast to the well-studied canonical regulatory mechanisms, the way by which the recently discovered Src N-terminal regulatory element (SNRE) modulates Src activity is not yet well understood. Phosphorylation of serine and threonine residues modulate the charge distribution along the disordered region of the SNRE and may affect a fuzzy complex with the SH3 domain that is believed to act as an information transduction element. The preexisting positively charged sites can interact with the newly introduced phosphate groups by modulating their acidity, introducing local conformational restrictions, or coupling various phosphosites into a functional unit. In this paper we use pH dependent NMR measurements combined with single point mutations to identify the interactions of basic residues with physiologically important phosphorylated residues and to characterize the effect of these interactions in neighbor residues, thus providing insight on the electrostatic network in the isolated disordered regions and in the entire SNRE. From a methodological point of view, the linear relationship observed between the mutation induced pKa changes of the phosphate groups of phosphoserine and phosphothreonine and the pH induced chemical shifts of the NH groups of these residues provides a very convenient alternative to identify interacting phosphate groups without the need to introduce point mutations on specific basic residues.

biophysics↗

bioRxiv2023

CoCl2 triggered pseudohypoxic stress induces proteasomal degradation of SIRT4 via polyubiquitination of lysines K78 and K299

SIRT4 comprises together with SIRT3 and SIRT5 the mitochondrially localized subgroup of sirtuins. SIRT4 regulates via its NAD+-dependent enzymatic activities mitochondrial bioenergetics, dynamics (mitochondrial fusion), and quality control (mitophagy). Here, we address the regulation of SIRT4 itself by characterizing its protein stability and degradation upon CoCl2-induced pseudohypoxic stress that typically triggers mitophagy. Interestingly, within the mitochondrial sirtuins, only the protein levels of SIRT4 or ectopically expressed SIRT4-eGFP decrease upon CoCl2 treatment of HEK293 cells. Co-treatment with BafA1, an inhibitor of autophagosome-lysosome fusion required for autophagy/mitophagy, or the use of the proteasome inhibitor MG132 prevented CoCl2-induced SIRT4 downregulation. Consistent with the proteasomal degradation of SIRT4, the lysine mutants SIRT4(K78R) and SIRT4(K299R) showed significantly reduced polyubiquitination upon CoCl2 treatment and were more resistant to pseudohypoxia-induced degradation as compared to SIRT4. Moreover, SIRT4(K78R) and SIRT4(K299R) displayed increased basal protein stability as compared to wild-type SIRT4 when subjected to MG132 treatment or cycloheximide (CHX) chase assays. Thus, our data indicate that stress-induced protein degradation of SIRT4 occurs through two mechanisms, (i) via mitochondrial autophagy/mitophagy, and (ii) as a separate process via proteasomal degradation within the cytoplasm.

biochemistry↗